Optical Network Termination, FTTH, and Customer Premises Installation
Optical network termination, FTTH and customer premises installation are tested through PON architecture, optical power budgets, ONT checks and handover practice.
Core rules
- GPON (ITU-T G.984): 2.488 Gbit/s downstream at 1490 nm, 1.244 Gbit/s upstream at 1310 nm; 1550 nm may carry video overlay; 1625 nm is used for in-service OTDR testing through a filter. XGS-PON provides 10 Gbit/s symmetric.
- ODN: OLT → feeder fibre → splitter (1:8, 1:16, 1:32, 1:64) → distribution and drop cable → ONT/ONU. Splitter loss is roughly 10.5 dB (1:8), 13.8 dB (1:16), 17 dB (1:32), 20.5 dB (1:64).
- Use G.657A2 bend-insensitive drop cable indoors; SC/APC is standard for PON ports to meet return-loss requirements. Keep minimum bend radius and avoid stapling through the cable.
- ONT installation: mount in a ventilated place, connect fibre and LAN, check PON/LOS/LAN LEDs, verify receive power (GPON Class B+ sensitivity about −27 dBm), test throughput and Wi-Fi, label ports, earth as required.
- Customer handover: demonstrate service, explain power, warn against touching the fibre, record serial numbers and signal levels.
Worked example
A GPON link has a 28 dB budget. 1:16 splitter = 13.8 dB; 10 km feeder at 0.35 dB/km = 3.5 dB; four connectors at 0.3 dB = 1.2 dB; two splices at 0.1 dB = 0.2 dB. Total = 18.7 dB, leaving 9.3 dB margin. If OLT launch is +3 dBm, ONT receive is about −15.7 dBm, comfortably above −27 dBm sensitivity.
Traps
- Mating APC ONT ports with UPC patch cords.
- Dirty connector causing high loss; always inspect and clean.
- Using a 1:32 splitter on a budget designed for 1:16.
- Confusing LOS LED (loss of signal) with power LED.